Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash Flows from Operating Activities:
Net Income	$ 20,939	$ 98,821	$ 46,294
Plus (gain) loss from discontinued operations, net of taxes	0	(14,211)	181
Adjustments to reconcile net income to net cash provided by operation activities -
Depreciation, depletion, and amortization	247,178	221,230	162,572
Accretion of asset retirement obligation	5,121	4,570	3,956
Deferred income taxes	16,798	48,995	32,881
Stock-based compensation expenses	13,476	12,625	10,256
Other	976	2,143	1,563
Change in assets and liabilities-
(Increase) decrease in accounts receivable	3,235	(12,625)	(6,691)
Increase (decrease) in accounts payable and accrued liabilities	(2,102)	10,134	472
Increase (decrease) in income taxes payable	82	(73)	247
Increase in accrued interest	8,903	1,449	7,265
Cash provided by operating activities – continuing operations	314,606	373,058	258,996
Cash used by operating activities – discontinued operations	0	(2)	(41)
Net Cash Provided by Operating Activities	314,606	373,056	258,955
Cash Flows from Investing Activities:
Additions to property and equipment	(757,755)	(505,332)	(353,648)
Proceeds from the sale of property and equipment	528	50,284	133
Cash used in investing activities – continuing operations	(757,227)	(455,048)	(353,515)
Cash provided by investing activities – discontinued operations	0	5,000	5,000
Net Cash Used in Investing Activities	(757,227)	(450,048)	(348,515)
Cash Flows from Financing Activities:
Proceeds from long-term debt	157,500	247,890	0
Net proceeds from bank borrowings	39,400	0	0
Net proceeds from issuances of common stock	1,712	2,151	142,917
Purchase of treasury shares	(2,805)	(3,393)	(1,828)
Payments of debt issuance costs	(4,712)	(4,327)	(3,631)
Cash provided by financing activities – continuing operations	191,095	242,321	137,458
Cash provided by financing activities - discontinued operations	0	0	0
Net Cash Provided by Financing Activities	191,095	242,321	137,458
Net Increase (decrease) in Cash and Cash Equivalents	(251,526)	165,329	47,898
Cash and Cash Equivalents at Beginning of Period	251,696	86,367	38,469
Cash and Cash Equivalents at End of Period	170	251,696	86,367
Supplemental Disclosures of Cash Flows Information:
Cash paid during period for interest, net of amounts capitalized	46,911	32,078	24,622
Cash paid during period for income taxes	$ 248	$ 1,770	$ 200